This invention relates to an external aquarium filter, and, more particularly, to a canister filter, which is positioned externally of an aquarium tank.
Numerous types of filtering apparatus are available for aquarium filtration. Generally, it is desired that the apparatus should perform all three of the basic types of filtration. Specifically, the filter should perform, mechanical filtration, which removes the suspended solid material from the water. It should also achieve chemical filtration, which removes dyes and other colorants, as well as certain inorganic substances. The third, and probably most important filtration to be achieved is that of biologic filtration, which removes certain organic waste products by means of naturally occurring bacteria living attached to the filter material.
One type of aquarium filter is the external aquarium filter which typically has a housing that hangs suspended from a wall of the aquarium tank. The contaminated water is extracted from the aquarium tank and supplied to the filter. Through the use of various filtering materials in the filter housing, the water is filtered and passes to a clean water chamber. From there, the water flows back into the aquarium tank, providing clear water to the aquarium, as well as providing the necessary aeration needed into the tank.
The type of filtering material typically utilized in external aquarium filters generally includes a layer of charcoal with an additional layer of glass wool or polyester fibers placed above the charcoal.
Another type of external aquarium filter is typically referred to as the canister filter. Such filters are generally placed adjacent to or beneath the aquarium tank and are typically in the form of a tall cylindrical can. Through a siphon arrangement, the water is drawn out of the aquarium tank and passes through a port in the bottom of the canister filter. The water then flows upwardly through a filtering material to the top of the canister. From there, the water flows out of the top of the canister and back into the aquarium tank. While a siphon arrangement can be used to extract the contaminated aquarium water, additional pumping is required to maintain a continuous flow and return the water back to the aquarium tank.
The typical canister filter utilizes the same type of filter material as other external filters, including layers of charcoal, glass wool, or polyester fibers. Additionally, ceramic tubes of short length are typically placed in the canister filter in order to provide additional surface area for the growth of aerobic bacteria within the canister filter in order to enhance biological filtration.
An improved external aquarium filter has been provided in U.S. Pat. No. 4,265,751, assigned to the assignee of the present invention. In that patent, there is provided a canister type filter which is flat, elongated, and can receive a layer of open cell, reticulated, foam plastic material, such as polyurethane foam as the filtering material. Because of the very large surface area provided by the foam material, and because of the thin, flat nature of the filter, there is a very large surface area provided for filtering, thereby increasing the area for the growth of the necessary bacteria required for biological filtration of the toxic waste in the contaminated water.
In the canister type filter of the aforementioned patent, the clear water chamber is at the top of the canister, and the contaminated water chamber is beneath the filter material. As a result, the filtering is from the bottom upwards, through the foam material. Therefore, the bottom contaminated water chamber also acts as a settling chamber where the larger particles of detritus and food can settle. As a result, the dirt particles will not clog the pores of the foam and will not impair the functioning of the filter bed. On the other hand, the solid particles will fall against the bottom of the filter housing, leaving the face of the filter bed free for the flowing water. Since large particles of debris do not clog the filter bed, a very fine foam can be used, which would increase the surface area for bacterial attachment and, therefore, increase the carrying capacity of the filter bed immensely. This lack of accumulation of debris along the surface and within the pores of the foam permits a great improvement over the prior art canister type filters.
In the aforementioned filter, the housing is constructed substantially of rectangular configuration, being elongated and flat. Opposing ribs, respectively depending from the top surface and projecting upward from the bottom surface, approach each other with a space therebetween defining a channel in which the layer of foam can be inserted. To insert and remove the foam, one end of the housing is opened to extract the foam when cleaning or replacement is needed and to insert another sheet of foam or reinsert the same foam after it has been cleaned.
Generally, with all types of canister filters, since the filtering is from the bottom upwards through the filter bed, the inlet port is provided at the lower end of the canister housing. The outlet is adjacent the upper end. Any pump that is utilized is externally provided.
While such canister filters have been useful, and especially the aforementioned external filter of U.S. Pat. No. 4,265,751, alternate structures could provide additional manufacturing benefits and also facilitate insertion and removal of the foam filtering material.